Thermal control means for a cleaner assembly



y 1970 l R. c. LAGERSTROM 3,510,904

THERMAL CONTROL MEANS FOR A CLEANER ASSEMBLY Filed Nov. 24, 1967 2 Sheets-Sheet l May 12, 1970 I R. c. LAGERSTROM ,9

THERMAL CONTROL MEANS FOR A CLEANER ASSEMBLY v Filed Nov. 24, 1967 Z'Sheets-Sheet 2 United States Patent Office 3,510,904 Patented May 12, 1970 3,510,904 THERMAL CONTROL MEANS FOR A CLEANER ASSEMBLY Robert C. Lagerstrom, Normal, Ill., assignor to National Union Electric Corporation, Stamford, Conn., a corporation of Delaware Filed Nov. 24, 1967, Ser. No. 685,531 Int. Cl. A47] /00 U.S. Cl. 15319 3 Claims ABSTRACT OF THE DISCLOSURE Disclosed herein is a suction cleaner assembly having a fan for drawing air entrained materials into the cleaner assembly and a thermally responsive device mounted in 'a path of air flow from the fan for sensing when the temperature of the air exceeds a predetermined temperature and for disabling the fan when the predetermined temperature is exceeded to protect the suction cleaner assembly against overheating.

Vacuum or suction cleaners commonly use a fan assembly or suction unit to draw air entrained dirt and other materials into a filter bag. The filter ba-g removes the entrained dirt and other materials from the air as the air is drawn through the porous walls of the filter bag. Asdirt and other materials accumulate in the filter bag, the dirt and other materials clog the pores or minute openings in the walls of the bag and block the fiow of air through the bag. When the flow of air through the bag is blocked, a motor in the fan assembly tends to overheat because of the greatly reduced air flow. Of course, the motor is usually damaged when it becomes overheated. This overheating becomes particularly serious when the motor is mounted on a housing which is weakened structurally when overheated, for example, a housing of thermoplastic material.

Therefore, it is an object of this invention to provide a suction cleaner assembly having a thermally responsive device or sensor unit for sensing when the cleaner assembly is overheating and for disabling the cleaner assembly when it becomes overheated.

Another object of this invention is to provide a suction cleaner assembly having a plastic housing which is protected against overheating by a thermally responsive device which disables a suction unit mounted on the housing when the housing begins to overheat.

Another object of this invention is to provide a suction cleaner assembly including a thermally responsive device mounted in a flow of exhaust air from a fan assembly for sensing when the cleaner assembly is being overheated.

These and other objects and features of the invention will become more apparent upon a consideration of the following detailed description taken in connection with the accompanying drawings wherein:

FIG. 1 is a partially broken away top plan view of a cleaner assembly forming an illustrative embodiment of the invention;

FIG. 2 is an enlarged sectional view, taken along the line 2-2 of FIG. 1, further illustrating the structure of the cleaner assembly;

FIG. 3 is a top plan view of a base plate assembly used in the cleaner assembly of FIG. 1;

FIG. 4 is an elevational view, on an enlarged scale, of a mounting for a thermally responsive device or thermostat which is a component of the base plate assembly of FIG. 3; and

FIG. 5 is a schematic illustration of control circuitry for the cleaner assembly of FIG. 1.

Briefly described, a vacuum or suction cleaner assembly 10, forming an illustrative embodiment of the invention, includes a suction unit or motor and fan assembly 12 for drawing fluid or air entrained dirt and other particles through a hose 14 into a filter bag 16. The air is exhausted from the cleaner assembly through a port or aperture 18 in a base plate assembly 20. A thermally responsive device or thermostat 22 is mounted on the base plate assembly 20 in a path of flow of air from the suction unit 12. The thermostat 22 senses when the temperature of the air from the suction unit exceeds a predetermined temperature and interrupts a circuit for energizing the suction unit 12 when the temperature is exceeded to protect the cleaner assembly against damage due to overheating. In the present instance, the thermostat is particularly advantageous since the suction unit 12 is mounted in a casing or housing 26 formed of a molded thermoplastic material which fuses or softens if the suction unit is overheated for an extended period of time. An indicator or warning light 28 (see FIG. 2) is connected to the thermostat 22 to indicate to an operator when the suction unit 12 is overheated.

More fully described, the cleaner assembly 10 includes a base section 30 (see FIG. 2) which is integrally molded of a suitable thermoplastic material, such as a commercially available ABS plastic. A cover section 32 is also molded of a thermoplastic material such as polystyrene and is connected to the base section 30 by a hinge assembly 34. The base section 30 and cover section 32 enclose the suction unit 12 which is mounted, as by screws 37, on an annular support or mounting wall 38 of the base section. The base plate assembly 20 is also connected to the base section 30 to form an exhaust cavity or chamber 40 into which air flows from the suction unit 12.

The suction unit 12 includes a fan 44 which is driven by an electric motor 46. When the motor 46 is energized, the fan 4 draws air entrained dirt and foreign particles through the hose 14 (see FIG. 1) into the filter bag 16. The dirt and foreign particles are trapped in the filter bag as the air flows through the porous sides of the filter bag. The filtered air then flows into the fan 44 and through the motor 46 to the exhaust chamber 40. As the air flows through the motor, heat is transferred from the motor 46 to the air to cool the motor. The relatively warm air is exhausted from the exhaust chamber 40, through the port 18 in the base plate assembly 20, to the surrounding atmosphere. The structure of the housing 26 and base plate assembly 20 is disclosed more fully in application Ser. No. 683,435 filed on Nov. 13, 1967, by Harold W. Schaefer.

When the flow of air through the suction unit 12 is blocked, by dirt clogging the porous sides of the filter bag 16 or other means, the motor 46 tends to overheat. Heat from the motor 46 will then be conducted to the plastic mounting wall 38 of the base section 30. As the plastic mounting wall 38 is heated to a relatively high temperature, the plastic loses its strength and ability to withstand the torque exerted by the motor 46. In the present instance, the base section 30 and mounting wall 38 are formed of a thermoplastic which tends to soften or fuse when overheated. Consequently, overheating of the motor 46 is especially serious with the thermoplastic base section 30 since the torque exerted by the motor 46 can readily twist the motor loose if the mounting wall begins to overheat stops the generation of heat by the motor before sufficient heat is conducted to the housing 26 to weaken or otherwise damage the housing.

In the present instance, the thermostat 22 is mounted on a support member or bracket 54 of the base plate assembly 20. The thermostat 22 is positioned on the bracket 54 directly beneath and spaced apart from the motor 46 in a path of flow of exhaust air from the motor. Positioning the thermostat 22 in the path of flow of air from the motor 46 enables the thermostat to immediately sense when the motor is beginning to overheat. This high degree of sensitivity results from the fact that the air is used to cool the motor as it flows through the motor. Consequently, as soon as the motor 46 begins to overheat the air is heated above its normal temperature as it flows through the motor and subsequently actuates the thermostat 22.

The thermostat 22 is of the bimetallic type and is actuated to an open position at a temperature of approximately 165 F. The thermostat is actuated to the closed position at a temperature of slightly above 120 F. The difference between the opening and closing temperatures for the thermostat 22 insures that the motor 46 and housing 26 are relatively cool before the motor is again energized after it has once started to overheat. Of course, the preceding operating or actuation temperatures are to be considered as merely being illustrative of one embodiment of the invention and the invention should not be considered as restricted to the particular temperatures given.

When the suction unit 12 begins to overheat and is disabled by the thermostat 22, an operator of the disabled cleaner assembly 10 will want to know why the cleaner assembly was disabled. Therefore, the indicator light 28 is included in the circuitry 50 (see FIG. and is mounted on the base section 30 of the housing 26 (see FIG. 2) where it can be easily seen by an operator of the cleaner assembly. The indicator light 28 is of the well known, commercially available, high resistance type and is connected in parallel with the thermostat 22 by leads 60 and 62. When the thermostat 22 is in the closed position, the relatively high resistance of the indicator light 28 and low resistance of the thermostat 22 results in most of the current flowing through the thermostat 22 while a very small amount of current flows through the indicator light 28. This small amount of current is insufiicient to energize the indicator light 28. However, when the cleaner assembly begins to overheat and the thermostat 22 moves to the open position, current cannot flow through the thermostat 22 and must flow through the leads 60 and 62 to energize the indicator light 28. It should be noted that the relatively high resistance of the indicator light 28 limits the flow of current to an amount which is insufiicient to energize the motor 46 when the thermostat is in the open position.

The circuitry 50 also includes a plug 64 and a cord 66 which are indicated schematically in FIG. 5. The cord 66 has a relatively long length and is connected to a cord reel assembly 70 (see FIGS. 2 and 4) which is mounted on the support bracket 54 by a central spindle or connector 71. The cord reel assembly 10 includes a central sheave or drum which cooperates with a spring (not shown) in a known manner to wind up the cord 66 when an actuator lever 72 is depressed. The mounting of both the cord reel assembly 70 and the thermostat 22 on the support bracket 54 enables the base plate assembly to be completely assembly with the thermostat connected to the cord 66 before the base plate assembly is mounted on the casing or housing 26.

The plug 64 is connected by a lead 76 to an on-off or power control switch 74 mounted on the base plate assembly 20 (FIG. 2). The switch 74 is connected in series witht he motor 46 and thermostat 22 by leads 78 and 80. The thermostat 22 is connected to the plug 64 by a lead 82 to complete the circuitry 50. Thus, the

motor 46 is energized only when both the switch 74 and thermostat 22 are closed. When the thermostat 22 is open, the high resistance indicator light 28 limits the flow of current to a value which is sufiicient to energize the indicator light 28 and insufficient to energize the motor 46. Of course, when the switch 74 is open, neither the indicator light 28 nor the motor 46 can be energized.

During operation of the cleaner assembly 10, the plug 64 will be connected to a suitable source of electrical energy and the motor 46 of the suction unit 12 will be energized upon actuation of the on-off switch 74 to the closed position. The fan 44 will then be operated by the motor 46 to draw air entrained dirt and other particles into the filter bag 16 in the housing 26. The air will be drawn through the porous sidewalls of the filter bag 16 into the fan 44, the dirt and other particles being trapped within the filter bag 16. The filtered air will flow from the fan through the motor 46, into the exhaust chambers 40 and out the exhaust port 18 to the surrounding atmosphere.

The thermostat 22 is mounted in the exhaust chamber 40 in a path of flow of air from the motor 46 so that the thermostat 22 will sense when the air from the motor exceeds a predetermined temperature. If the suction unit 12 begins to overheat, due to an accumulation of dirt in the filter bag 16 or some unforeseen malfunction, the air flowing through the suction unit 12 will be heated and, when the air exceeds the predetermined temperature, the thermostat 22 will be actuated to the open position. When the thermostat 22 is actuated to the open position, the motor 46 will be disabled and the indicator light 28 will be energized to indicate that the cleaner assembly 10 has started to overheat. When the temperature of the air in the exhaust chamber has fallen below a predetermined temperature and the cleaner assembly 10 has cooled back to a normal or acceptable operating temperature, the thermostat 22 will move from the open position to the closed position to enable the motor 46 to again be energized. Thus, the thermostat 22 protects the thermoplastic housing 26 against being overheated, that is the thermostat 22 prevents the housing 26 from being heated to a temperature at which the housing will have insufficient strength to support the suction unit 12.

In the present embodiment of the invention it has been found to be particularly advantageous to mount the thermostat 22 in a spaced apart relationship with both the housing 26 and the suction unit 12 so that the thermostat 22 is in the path of flow of air from the suction unit 12 and is operative when the air from the suction unit exceeds a predetermined temperature. Of course, a thermostat for a vacuum cleaner could, if desired, be mounted directly on the cleaner housing or could also be included in the motor. However, a cleaner assembly having a combination motor and thermostat is both difficult and expensive to service since if either the thermostat or motor should fail, it is necessary to replace both the motor and thermostat with a particular combination motor and thermostat. The mounting of the thermostat 22 on the base plate assembly 20, in accordance with the present invention, facilitates easy and rapid replacement of the thermostat.

In view of the foregoing remarks it can be seen that I have provided a suction cleaner assembly 10 having a plastic housing 26 which is protected against overheating by a thermally responsive unit or thermostat 22. The thermostat 22 is mounted in a path of flow of exhaust air from a fan and motor assembly or suction unit 12 to disable the motor 46 when the air exceeds a predetermined temperature indicative of an overheating of the motor. An indicator light 28 has been provided to indicate to an operator of the cleaner assembly 10 when the suction unit 12 is disabled by the thermostat 22.

What is claimed is:

1. In a suction cleaner having a casing with an air 6 inlet and filter means connected to the inlet, the imsaid-base plate assembly being adapted to be completely provement which comprises, in combination: assembled with said control switch and said thermala support portion on the casing, said casing including 1y responsive device connected in said circuitry said support portion being formed of a thermobefore said base plate assembly 1s mounted on said plastic material having a tendency to soften at an 5 casing. elevated temperature; 2. The structure of claim 1 further charactenzed 1n a motor-fan unit connected to said support portion; that said base plate assembly includes a bracket member a base plate assembly connected to said casing and extending across said exhaust chamber and having said having a portion spaced fro s id support portion thermally responsive device mounted thereon.

of said casing and defining th bet e an exhaust 10 3. The structure of claim 2 further characterized in chamber, said b s plate assembly h i an exhaust that said thermally responslve device is secured to one air outlet, and said motor-fan unit being arranged Side of said bracket facing said motor-fan P a a r to direct filtered air into said exhaust chamber for reel is rotatably supported on the pp Side of Sand di h from id l bracket, and said electrical circuitry includes a cord said base plate assembly including a control switch WQIIIId 011 Said cord feel for fe the motor of mounted thereon and a thermally responsive device Bald motor-fall unit to a Source Of decimal ymounted thereon, said thermally responsive device being positioned wholly within said exhaust chamber References C'ted in spaced relation from said motor-fan unit and in UNITED STATES PATENTS the Path Of flow Of all from Said motor-fan unit; 2 97 73 Hansen 2,625,239 1/1953 Senne 55-217 eleqtrwal q t y connectmg l t e ma y respo 2,997,728 8/1961 Gaudry 15 323 sive de-vlce w1th the motor of said motor-fan unit 3,334,370 8/1967 Boyd 15 327 lfOl' shutting off the motor when the temperature of 3 375 541 4/ 1968 Fromknecht 3 7 the air from said motor-fan unit exceeds a predeu termined temperature upon clogging of the filter ROBERTW MICHELL,P -imary E i means and thereby preventing failure of the connection between said motor-fan unit and said sup- US. Cl. X.R.

fgfiafigrtlon due to overheating and softening of 15 323, 217 

